A late Pleistocene–Holocene noble gas paleotemperature record in southern Michigan
نویسندگان
چکیده
[1] Noble gas temperatures (NGTs) and C derived ages in groundwaters of the Michigan Basin reveal a ground temperature of 1 C toward the end of the Last Glacial Maximum (LGM) suggesting that groundwater recharge occurred under the Laurentide Ice Sheet (LIS) cover. In addition to the general warming observed since the LGM, the NGT record indicates an abrupt warming event between 12.8 and 11.1kyrs BP, correlative to the Bølling-Allerød (BOA) warm phases. Ice-sheet-linked changes in freshwater delivery to the North Atlantic, together with changes in the North Atlantic Deep Water (NADW) circulation are possible causes of such abrupt climate shifts in northeastern US. Pleistocene waters yielding the lowest NGTs have the highest dO and dD values, suggesting an atmospheric circulation pattern distinct from today, with a stronger moisture component from the Gulf of Mexico, possibly due to the presence of the LIS which weakened the Pacific westerly flow.
منابع مشابه
Noble gases and stable isotopes in a shallow aquifer in southern Michigan: Implications for noble gas paleotemperature reconstructions for cool climates
[1] Noble gas data from the Glacial Drift, the shallowest aquifer in southern Michigan confirm findings by Ma et al. (2004) that modern noble gas temperatures (NGTs) are systematically below the current mean annual air temperature (MAAT) which, in turn, is similar to the ground temperature of these recharge waters. By tracking noble gas concentrations as well as stable isotope ratios through an...
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متن کاملReply to comment by Klump et al. on ‘‘Noble gases and stable isotopes in a shallow aquifer in southern Michigan: Implications for noble gas paleotemperature reconstructions for cool climates’’
[1] In their comment, Klump et al. [2006], hereinafter referred to as KBK, make three main points concerning Hall et al. [2005]: (1) that the model of excess air that accounts for fractionation via the mechanism of diffusive loss should have produced significant changes from normal isotopic ratios; (2) the suggestion that the presence of excess He in the gas phase in the unsaturated zone is inc...
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